The present invention relates to a video tape recorder and, more particularly, to apparatus and method for recording and reproducing a video signal to and from a record medium having means for maintaining synchronous color framing and/or synchronous groups of pictures during an editing operation.
As is known, a composite video signal (e.g., an NTSC signal or a PAL signal) in MPEG-based decoding systems is digitized to produce a digital video signal and the digital video signal is compressed to form groups of pictures (GOP) comprised of both intraframe and interframe video signals. The compressed video signal then is recorded on helical tracks on a magnetic tape and a control (CTL) signal, which is provided to control the tape traveling speed during a playback operation, is recorded on a control track of the magnetic tape.
During a playback operation, the compressed video signal is reproduced from the magnetic tape, the reproduced data (i.e., signal) is expanded to produce non-compressed digital video data, the non-compressed data is converted to an analog composite video signal, and the composite video signal is supplied to a video monitor which displays the video picture. Unfortunately, the quality of the reproduced and subsequently decoded video signal is deteriorated as compared to the originally supplied signal that was digitized, encoded and recorded on the magnetic tape. One cause for such deterioration is the product of Y/C separation wherein a portion of the chroma (C) signal remains as part of the luminance (Y) signal after separation. Color framing (CF) sequence information, which is part of the chrominance portion of the video signal, remains in the luminance signal after Y/C separation and, thus, the original composite video signal cannot be properly reconstructed from the recorded digital data. Hence, there is frequency deterioration as well as other types of deterioration in the reproduced composite video signal.
Furthermore, when recorded digital data is edited, it is necessary to perform a so-called "disconnecting" and "reconnecting" of each GOP in order to properly edit the recorded digital data. The continuity (to be discussed) of the color framing (CF) sequence of the recorded as well as the newly-recorded (i.e., edited) signals should be maintained in order to provide a properly edited signal.
Still further, another problem encountered with prior art devices, such as discussed above, is their general inability to generate and provide a correct CF signal to externally coupled video processing devices. Such devices generally require that compressed video data be supplied thereto in synchronization with the CF signal, and since it is difficult to generate a correct CF signal from the reproduced video data, such synchronization is not easily carried out.